Briana saved $1.80
Further explanation
Algebraic expressions in mathematics are a combination of coefficients, numbers, variables, constants and arithmetic operations such as addition, subtraction, multiplication, and division.
Purchasing a backpack that cost $45 with a sales promotion of 20% off
[tex]\tt 20\%\times \$45=0.2\times 45=\$9[/tex]
[tex]\tt cost=\$45-\$9=\$36[/tex]
Purchasing a backpack that cost $42 with a sales promotion of 10% off
[tex]\tt 10\%\times \$42=0.1\times 42=\$4.2[/tex]
[tex]\tt cost=\$42-\$4.2=\$37.8[/tex]
Briana saved :
[tex]\tt \$37.8-\$36=\$1.8[/tex]
